Considerable evidence suggests postpartum thyroid disease (PPTD) is autoimmune in origin. Thyroid antibodies are positive in 2.8 to 18.7% of all postpartum women. The antibody titer predicts the likelihood of a woman developing clinical disease. Future studies should determine how to improve the utility of antibody testing. Postpartum enhancement of autoimmunity is not limited to thyroid diseases; flare-ups of systemic lupus erythematosus and an increase in DNA antibodies can occur. One woman with PPTD also developed a transient sicca syndrome, suggesting immunologic changes postpartum may induce an autoimmune exocrinopathy. Racial differences exist for some autoimmune diseases. One study reported 8.8% of Caucasians, but only 2.5% of African-American women were antibody positive two days postpartum. This protocol will follow 1,280 women (640 Caucasians, 640 African-American) from first pergnancy visit until six months postpartum. Main end-points are serum TSH, thyroid peroxidase, thyroglobulin, and Ro and La antibodies. It is expected that 64-102 women (5-8%) with thyroid autoimmunity be identified. Approximately half (32-51) women will develop clinical disease and benefit from diagnosis and treatment. The primary end-point is to see whether there is a significant difference in the frequency of postpartum thyroid diseases between Caucasian and African-American women. A second end-point will be to assess whether postpartum women develop immunologic evidence of Sjogren's disease. The results will help to define better risk guidelines and provide improved counseling to women.